Alkyl esters or organic acids,such as stearyl malate,as antifoggants

ABSTRACT

ALKYL ESTERS OF ORGANIC ACIDS, SUCH AS STEARYL MALATE, ARE USED AS A STABILIZER AND FOG INHIBITOR FOR PHOTOGRAPHIC SILVER HALIDE.

U.S. Cl. 96-109 13 Claims ABSTRACT OF THE DISCLOSURE Alkyl esters of organic acids, such as stearyl malate, are used as a stabilizer and fog inhibitor for photographic silver halide.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to photography. In one aspect, this invention relates to the stabilization of photographic silver halide layers against spontaneous fog Without seriously affecting the photographic sensitivity of said silver halide layers.

Description of the prior art It is well-known that photographic silver halide on storage tends to lose sensitivity and to become spontaneously developable without exposure to light. The detectable amount of silver salt reduced during development of those areas where there is no exposure is commonly referred to as fog, and more specifically chemical fog where it is desirable to distinguish between it and the effects of accidental exposure to radiation.

Fog depends upon both the particular emulsion and the conditions of development. For a given emulsion, fog increases with the degree of development. At constant development conditions, fog generally increases with the temperature, time and relative humidity of storage conditions.

It is known that certain mercaptans, particularly those compounds having mercapto substitution on a heterocyclic ring, and certain organic disulfides have an antifoggant and stabilizing effect when incorporated in photographic silver halide emulsions. For example, U.S. Pat. 2,440,110 discloses organic disulfides used in combination with sulfinic or selenic acids or their salts, U.S. Pat. 2,819,965 describes the use of s-triazines having a carboxymethylmercapto substituent, U.S. Pat. 2,935,404 describes bis(s-triazolo[4,3-a]pyrimidine) disulfides, and British Pat. 819,370 describes mercapto-1,2,4-triazines. Many of the prior art compounds are objectionable either because they are not effective antifoggants unless used in combination with other materials, While other compounds have a desensitizing effect at concentrations wherein said compounds are most effective as antifoggants. It is therefore desirable to obtain compounds which are effective antifoggants for photographic silver halide elements Without effecting desensitization.

SUMMARY OF THE INVENTION In accordance with this invention, it has been found that significantly enhanced stability against chemical fog in photographic silver halides can be obtained while not seriously effecting a decrease in their photographic sensitivity. The enhanced stability and control over chemical fog is obtained through the use of compounds not known, heretofore, to be useful as antifoggants.

It is the object, according to one aspect of this invention, to provide stabilized photographic silver halides.

It is another aspect of this invention to provide a method for stabilizing silver halides.

It is yet a further object to stabilize silver halide eleinited States Patent DESCRIPTION OF THE PREFERRED EMBODIMENTS It has been found that certain alkyl esters of organic acids act as strong antifoggants and stabilize photographic silver halides without causing a serious reduction in their photographic sensitivity. Alkyl esters which are illustrative of this invention are: di-(acetyl malate) of glycerol monostearate, monosuccinate of diglycerol monostearate, monosuccinate of dipropylene glycol monostearate, diethylene glycol monostearate and those alkyl esters having the general formula:

0 R4 R5 0 [Ot tH (tH) 1 THE wherein R is H, alkyl radicals containing 1-30 carbon atoms such as the lower alkyls as illustrated by methyl and ethyl and the higher alkyls as illustrated by nonacosyl and triacontyl, the preferred alkyl radicals being that derived from steric alcohol and steric acid, or aryl, such as phenyl; R is H, alkyl such as methyl, ethyl and propyl, aryl as previously described, OH, halogen such as chlorine, bromine and iodine 0 oiin keto, COOH or O 0-(3-11 Oi JCH2( /HCOOH each of R R R and R is H, alkyl such as methyl,

ethyl and propyl, aryl such as previously described, OH, halogen as previously described keto or COOH; each of x, y and z is 0 or 1, at least one of x and y being 1; each of a and b is O, 1 or 2; each of n 11 and n is 0, 1, 2 or 3 and R is alkyl such as methyl, ethyl and propyl.

Preferred compounds of this invention are represented by the above general formula in the instances wherein: xis0,yis1,n isl,n is1andn is1;xis1,yis0,n is 0,11 is 1 andn is0;andxis0,yis 1,n is O,n is1 and n is 1.

A particularly preferred group of compounds which are represented by the above general formula is:

stearyl malate,

stearyl acetyl malate,

monosuccinate of 1,3-butandiol monostearate, stearyl succinate,

monosuccinate of propylene glycol monostearate, monosuccinate of glycerol monostearate, monomalate of glycerol monostearate, monoacetyl malate of glycerol monostearate, and monosuccinate of ethylene glycol monostearate.

The compounds used in this invention are known and are conveniently prepared by methods well-known in the art.

The concentration of the stabilizing compound can vary considerably depending on various factors such as: the effects desired, silver content of the photographic element, the nature of the particular silver halide, the degree of ripening, the location of the stabilizer in relation to the silver halide, the particular stabilizer, etc. In general, a concentration in the range of about 1 gram to about 50 grams of stabilizer per mole of silver halide is useful. A preferred range is from about 5 grams to about 32 grams of stabilizer per mole of silver halide. In accordance with the invention, one may use the higher concentrations without inducing a reduction in photographic sensitivity. The optimum concentration of stabilizer for a particular photographic system can be determined through techniques well-known in the art.

The stabilizing addenda can be added in a variety of ways and at various stages in the preparation of the photographic system. The stabilizers may be incorporated directly into silver halide layers, preferably before the final digestion operation, in the case of emulsions, and after the silver halide grains are substantially in their final size and shape. The addenda may be added to a layer adjacent to the silver halide layer. The solvents in which the stabilizers may be dissolved are restricted to those that are not harmful to the silver halide layer, and in accordance with the general practice organic solvents and diluents are preferred.

The light-sensitive silver halide emulsions comprising the antifoggants of this invention can contain addenda such as gelatin plasticizers, coating aids and hardeners such as the aldehyde-type hardeners, e.g., formaldehyde, mucochloric acid, glutaraldehyde bis(sodium bisulfite), maleic dialdehyde, and aziridines, dioxane derivatives, vinylsulfonylethers and oxypolysaccharides. Sensitizing dyes useful in sensitizing such emulsions are described, for example, in U.S. Pats. 2,526,632 of Brooker and White issued Oct. 24, 1950, and 2,503,776 of Sprague issued Apr. 11, 1950. Spectral sensitizers which can be used are the cyanines, merocyanines, complex (trinuclear) cyanines, complex (trinuclear) merocyanines, styryls and hemicyanines. Developing agents can also be incorporated into the emulsion if desired or can be contained in a separate underlayer.

The stabilizing addenda employed in the practice of this invention can be used in various kinds of photographic emulsions. In addition to being useful in orthochromatic, panchromatic and infrared emulsions, they are also useful in X-ray and other non-spectrally sensitized emulsions. They can be added to the emulsions before, simultaneously or after any spectrally sensitizing dyes that may be used. They are particularly effective in sulfur and gold sensitized silver halide emulsions. Various silver salts can be used as sensitive salts, including, for example, silver bromide, silver iodide, silver chloride, silver chlorobromide, silver bromoiodide or silver chloroiodide and the like. The silver halides can be those which form latent images predominantly on the surface of the silver halide grains or those which form latent images inside the silver halide crystals such as described in U.S. Pat. 2,592,250 of Davey and Knott issued Apr. 8, 1952. The subject addenda can be used in emulsions intended for color photography, for example, emulsions containing color-forming couplers or emulsions to be developed by solutions containing couplers or other color-generating materials; emulsions of the mixed-packet type such as described in U.S. Pat. 2,698,794 of Godowsky issued Ian. 4, 1955; in silver dye-bleach systems; and emulsions of the mixedgrain type such as described in U.S. Pat. 2,592,243 of Carrol and Hanson issued Apr. 8, 1952.

In the preparation of the silver halide dispersions employed for preparing silver halide emulsions there can be employed as the dispersions agent, or binders as they are known in the art, for the silver halide in its preparation, gelatin or some other colloidal material such as modified gelatin, colloidal albumin, a cellulose derivative, 2. polyvinyl compound, acrylamide polymers, etc., although gelatin is preferred. Mixtures of these binding agents can also be used. The binding agents for the emulsion layer of the photographic element can also contain dispersed polymerized vinyl compounds. Such compounds are disclosed, for example, in U.S. Pats. 3,142,568 of Nottorf issued July 28, 1964; 3,193,386 of White issued July 6, 1965; 3,062,674 of Houck, Smith and Yudelson issued Nov. 30, 1965; and include the water-insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates and the like.

The photographic emulsions stabilized according to this invention can be coated on a wide variety of supports. Typical supports include those generally employed for photographic elements, as exemplified by cellulose nitrate film, cellulose ester film, poly(vinyl acetal) film, polystyrene film, poly(ethylene terephthalate) film and related films of resinous materials as well as glass, paper, metal, wood and the like. Supports such as paper that are coated with alpha-olefin polymers, particularly polymers of alpha-olefins containing 2 or more carbon atoms, as for example, polyethylene, polypropylene, ethylene-butene c0- polymers and the like, can also be employed.

Photographic silver halide elements comprising the antifoggants can also contain speed-increasing compounds such as quaternary ammonium compounds, polyethylene glycols or thioethers. Frequently, useful effects can be obtained by adding the aforementioned speed-increasing compounds to the photographic developer solutions mstead of, or in addition to, the photographic layer.

Silver halide emulsions containing the antifoggants of the instant invention can be sensitized using any of the well-known techniques in emulsion making, for example, by digesting with naturally active gelatin or various sulfur, selenium, tellurium compounds and/or gold compounds. The emulsions can also be sensitized with salts of noble metals of Group VIII of the Periodic Table which have an atomic weight greater than 100.

Silver halide emulsions containing the antifoggants of the invention can be used in. diffusion transfer processes which utilize the undeveloped silver halide in non-image areas of the negative to form a positive by dissolving the undeveloped silver halide and precipitating it on a receiving layer in close proximity to the original silver halide emulsion layer. Such processes are described in U.S. Pats. 2,352,014 of Rott issued June 20, 1944; 2,543,181 of Land issued Feb. 27, 1951; and 3,020,155 of Yackel, Yutzy, Foster and Rasch issued Feb. 6, 1962. The emulsions can also be used in dilfusion transfer color processes which utilize a diffusion transfer of an imagewise distribution of developer, coupler or dye from a light-sensitive layer to a second layer while the two layers are in close proximity to one another.

The following examples are included for a further understanding of the invention.

EXAMPLES I-XVIII Compounds of this invention, listed in the table below, are incorporated, at concentrations listed in the table, into separate samples of a high-speed gelatino silver bromoiodide photographic emulsion. Each emulsion sample is coated on a cellulose acetate film support at a coverage of 459 mg. of silver and 1040 mg. of gelatin per square foot. For comparison, film strips absent the compounds employed in this invention are also prepared. A sample of each film coating is exposed on a Eastman 1B sensitometer, processed for 5 minutes in Kodak DK-SO Developer, fixed, washed and dried. Separate samples of the film coating are incubated for 2 weeks at F. and 50% relative humidity before exposure and development.

The results of the sensitometric tests on the fresh and incubated samples are summarized in the table.

Two weeks incubation at 120 F., relative Fresh samples humidlty Stabilizing compounds Relative Relative (g./mole of Ag) speed Gamma Fog speed Gamma Fog Control 100 1. 64 15 54 1. 24

Control 100 1. 49 17 49 1. 15 68 G (19.8) 80 1. 25 12 71 1. 13 12 Control 100 1. 51 16 28 96 96 .0 87 l. 60 13 57 1. 23 37 100 1.60 12 53 1. 27 47 Control 100 1. 29 17 47 99 60 J (18) 7B 1. 22 12 62 1. 23 27 Control 100 1. 64 15 54 1. 24 60 31 83 1. 37 08 63 1. 45 23 1. 43 09 73 1. 22 18 Control 1. 64 15 54 1. 24 60 M (22.1) 97 1. 28 10 58 0.93 .39

No'rEs:

A. Stearyl malate. B. Stcaryl acetyl malate. C. Monosuccinate of 1,3-butandiol monostearate. D. Stearyl succinate. E. Monosuccinate of propylene glycol monostearate. F. Monosuccinate of glycerol monostearate. G. Monomalate of glycerol monostearate. H. Monoacetyl malate of glycerol monostearate. I. D-(acetyl malate) of glycerol monostearate. J. Monosuccinate of diglycerol monostearate.

K. Monosuccinate of dipropylene glycol monostearate. L. Monosuecinate of ethylene glycol monostearate. M. Diethylene glycol monostearate.

The examples, as summarized in table, show that the compounds of this invention are highly useful as stabilizers and fog inhibitors for photographic silver halide emulsions. It should be noted that fog is inhibited without any concurrent substantial loss, if any, in sensitivity of the silver halide emulsion. In the case of the incubated samples the speed of the treated emulsions is always greater than the non-treated samples. With respect to the fresh samples there was an insignificant loss in speed, if any.

The invention, it is seen, provides silver halide emulsions stabilized with the particular antifoggants not causing any deleterious effect upon speed or sensitivity.

The compounds of this invention, for example, diethylene glycol monostearate, monomalate of glycerol monostearate and the like are additionally useful as solvents for color-forming couplers in photographic silver halide emulsions. In a typical procedure, the color-forming coupler is dissolved in the solvent, i.e., an alkyl ester employed in this invention, and dispersed in a gelatin-silver halide emulsion according to the procedure disclosed in US. Pats. 2,322,- 027 of Jelly and Vittum issued June 15, 1943, and 2,801,- 171 of Fierke and Chechak issued July 30, 1957. The compounds of this invention can also be used as solvents for brighteners, UV. absorbers, etc.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

I claim:

1. A photographic element comprising a support, a silver halide layer and, as an addendum, at least one of di(acetyl malate) of glycerol monosterate, monosuccinate of diglycerol monostearate, monosuccinate of dipropylene glycol monostearate, diethylene glycol monostearate, or a compound having the general formula:

wherein R is H, alkyl or aryl; R is H, alkyl, aryl, OH, halogen,

keto, COOH or n 0 OCR1 o (U}CH2'-(|3HCO OH each of R R R and R is H, alkyl, aryl, OH, halogen,

o o R keto, or COOH, each of x, y and z is 0 or 1, at least one x ory being 1; each of a and b is 0, l or 2; each of n I1 and n is 0, 1, 2 or 3; and R is alkyl.

2. A photographic element as in claim 1 wherein said addenda is present at a stabilizing concentration of from about 1 to about 50 grams per mole of silver halide.

3. A photographic silver halide emulsion stabilized with at least one of di-(acetyl malate) of glycerol monostearate, monosuccinate of diglycerol monostearate, dipropylene glycol monostearate, diethylene glycol monostearate or a compound having the general formula:

wherein R is H, alkyl or aryl; R is H, alkyl, aryl, OH, halogen,

keto, COOH, and

OJR1 O ylCHzCH-Ji? O 011 each of R R R and R is H, alkyl, aryl, OH, halogen,

O O("3R keto or COOH; each of x, y and z is 0 or 1, at least one of x or y being 1; each of a and b is 0, l or 2; each of n n and n is 0, 1, 2 or 3; and R is alkyl.

4. A photographic emulsion as in claim 3 wherein x is 0, y is 1, n is 1, n is l and n is l.

5. A photographic emulsion as in cliam 4 wherein said stabilizer is monomalate of glycerol monostearate.

6. A photographic emulsion as in claim 3 wherein x is l, y is 0, n is 0, n is 1 and n is 0.

7. A photographic emulsion as in claim 6 wherein said stabilizer is stearyl malate.

8. A photographic emulsion as in claim 6 wherein said stabilizer is stearyl succinate.

9. A photographic emulsion as in claim 3 wherein x is 0, y is 1, n is 0, n is l and n is 1.

10. A photographic emulsion as in claim 9 wherein said stabilizer is monosuccinate of ethylene glycol monostearate.

11. A photographic emulsion as in claim 3 wherein said stabilizer is monosuccinate of dipropylene glycol monostearate.

12. A photographic emulsion as in claim 3 wherein said silver halide emulsion is a high-speed gelatino silver bromoiodide emulsion and said stabilizer is present in an amount of about grams to about 33 grams per mold of silver halide.

13. In a method for the stabilization of photographic silver halide elements against fog, the improvement comprising stabilizing said elements with one of di-(acetyl malate) of glycerol monostearate, monosuccinate of diglycerol monostearate, monosuccinate of dipropylene glycol monostearate, diethylene glycol monostearate and a compound having the general formula:

0 R R R a.

ROxCO -Y keto, -COOH or 0 OJLRI -O i )CHz-C lHC O OH each of R R R and R is H, alkyl, aryl, OH, halogen,

o -O("3R keto or -COOH; each of x, y and z is 0 or 1, at least one of x or y being 1; each of a and b is 0, 1 or 2; each n n and n is 0, 1, 2 or 3; and R is alkyl.

References Cited UNITED STATES PATENTS 2,378,204 6/1945 Fallesen 9666.5 3,033,680 5/1962 Milton 96109X 3,459,790 8/ 1969 Smith 96-109X JOHN T. GOOLKASIAN, Primary Examiner M. E. McCAMISH, Assistant Examiner US. Cl. X.R. 9666.5 

